Corporate estimated taxes are due on the 15th day of the 4th, 6th, 9th, and 12th months of the corporation’s tax year. For a calendar-year filer in 2026, that means April 15, June 15, September 15, and December 15. Any corporation expecting to owe $500 or more in federal income tax for the year has to pay in installments rather than settling up at filing time, and missing a due date or underpaying triggers a penalty the IRS almost never waives.
The Four Quarterly Due Dates
For a calendar-year corporation in 2026, the schedule is:
- 1st installment: April 15, 2026
- 2nd installment: June 15, 2026
- 3rd installment: September 15, 2026
- 4th installment: December 15, 2026
The spacing is uneven. Only two months separate the first payment from the second, then three months to the third, and three more to the fourth. First-time filers who assume a true quarterly rhythm get caught by the June deadline.
All four dates in 2026 fall on weekdays with no federal holiday conflicts, so nothing shifts. When a due date lands on a Saturday, Sunday, or legal holiday in other years, the payment is timely if made on the next business day.1Internal Revenue Service. Publication 509 (2026), Tax Calendars
Fiscal-year corporations use the same rule against their own year-end. A corporation with a June 30 fiscal year, for example, owes installments on October 15, December 15, March 15, and June 15. Always the 15th of the 4th, 6th, 9th, and 12th months of whatever tax year the corporation uses.1Internal Revenue Service. Publication 509 (2026), Tax Calendars
Which Corporations Have to Pay
Federal tax runs on a pay-as-you-go basis. A corporation must make estimated payments whenever it expects total tax liability of $500 or more for the year.2Office of the Law Revision Counsel. 26 USC 6655 – Failure by Corporation to Pay Estimated Income Tax C-corporations are the primary entities the rule reaches, because they’re taxed as separate legal entities from their owners.
S-corporations usually pass income through to shareholders and owe nothing at the corporate level. They still face estimated payment requirements in two narrow situations: tax on built-in gains from assets held before the S-election, and the passive investment income tax that hits when excess net passive income exceeds 25% of gross receipts while the corporation carries accumulated earnings and profits from its C-corporation years.3Office of the Law Revision Counsel. 26 USC 1375 – Tax Imposed When Passive Investment Income of Corporation Having Accumulated Earnings and Profits Exceeds 25 Percent of Gross Receipts The penalties for missing these are the same as for any other underpayment.
How Much Each Installment Has to Be
Project taxable income for the full year, apply the flat 21% corporate rate, subtract expected credits, and divide the result into four equal 25% installments.4Internal Revenue Service. Publication 542, Corporations IRS Form 1120-W is the worksheet built for this calculation. It stays in your records; you don’t file it with the IRS.5Internal Revenue Service. Instructions for Form 1120-W
The Prior-Year Safe Harbor
Rather than projecting current-year income, many corporations base installments on 100% of the tax shown on the prior year’s return. That approach protects against underpayment penalties no matter how much this year’s income grows, as long as the previous return covered a full 12-month tax year and showed some tax liability.5Internal Revenue Service. Instructions for Form 1120-W A short prior year, or a prior year with zero tax, disqualifies you from this method.
If Your Corporation Is “Large”
A corporation is large for estimated tax purposes if it (or any predecessor) had taxable income of $1 million or more in any of the three tax years immediately before the current one.2Office of the Law Revision Counsel. 26 USC 6655 – Failure by Corporation to Pay Estimated Income Tax Large corporations lose the prior-year safe harbor for most installments and must base payments on 100% of the current year’s expected liability.
One exception: a large corporation can still use the prior-year figure for the first installment. Any savings from doing so get recaptured in the second installment, which has to be increased by the same amount.2Office of the Law Revision Counsel. 26 USC 6655 – Failure by Corporation to Pay Estimated Income Tax If your corporation crossed the $1 million income mark at any point in the prior three years, plan on real-time projections for the June, September, and December payments.
When Income Is Uneven or Seasonal
A retailer that earns most of its income in the fourth quarter, or a construction business with seasonal peaks, would overpay heavily on equal 25% installments. Two alternative methods can lower or eliminate early-year payments.
The annualized income installment method recalculates each installment based on income actually earned through a cutoff point, then annualizes that figure. To elect it, file Form 8842 by the due date of the first required installment. The adjusted seasonal installment method is available when at least 70% of revenue concentrates in a six-consecutive-month period, measured against the average of the three preceding years.5Internal Revenue Service. Instructions for Form 1120-W Both methods run through Schedule A of Form 1120-W. If you use Schedule A for one payment date, you must use it for all four.6Internal Revenue Service. Instructions for Form 2220 – Underpayment of Estimated Tax by Corporations
How to Actually Submit the Payment
Corporations must pay through the Electronic Federal Tax Payment System (EFTPS).7Bureau of the Fiscal Service. Electronic Federal Tax Payment System Enrollment produces a Personal Identification Number, and new enrollments can take up to five business days to process.8Internal Revenue Service. EFTPS: The Electronic Federal Tax Payment System Don’t wait until the week a payment is due to set up the account.
Here’s the timing rule that catches the most corporations: payments must be scheduled by 8 p.m. Eastern Time the day before the due date. If the installment is due April 15, the EFTPS transaction has to be initiated by 8 p.m. ET on April 14. Submit at 9 p.m. on the 14th or any time on the 15th, and the payment is late, even if the money leaves your bank account the same day. Build that one-day lead time into your calendar.
What a Missed or Short Payment Costs
An underpayment triggers the penalty under Section 6655. It runs from the due date of each short installment until the earlier of the date you pay or the filing deadline for the return, calculated using the federal short-term rate plus three percentage points, adjusted quarterly. For the first quarter of 2026, that’s 7% for most corporations and 9% for large corporate underpayments.9Internal Revenue Service. Revenue Ruling 25-22, Section 6621 Determination of Rate of Interest
No penalty applies if total tax on the return is under $500.2Office of the Law Revision Counsel. 26 USC 6655 – Failure by Corporation to Pay Estimated Income Tax Above that, the IRS has almost no flexibility. Unlike most tax penalties, this one cannot be waived for reasonable cause. The only adjustment the IRS considers is where a corporation relied on incorrect written advice the IRS provided in direct response to the corporation’s own written inquiry.10Internal Revenue Service. Underpayment of Estimated Tax by Corporations Penalty That situation almost never arises, which makes hitting each due date on the correct amount unusually important.
State Deadlines Are Separate
Federal estimated tax is only part of the picture. Most states that impose a corporate income tax require their own estimated payments, and the rules don’t always mirror the federal system. Triggering thresholds typically range from $400 to $5,000. Underpayment penalties run from fixed 5% to 20% charges to annual interest of 7% to 14%. Some states track the federal quarterly schedule; others use different installment dates. Check your state’s department of revenue for the thresholds, deadlines, and payment methods that apply.